Copper base alloy



Patented Feb. 18, 1936 UNITED STATES 2,031,315 7 corrnn BASE ALLOY Herbert G. Jennison, Bridgeport, Conn.,assignor to The American Brass Company, Waterbury, Conn., a corporation of Connecticut No Drawing. Application August 5, 1933, Serial No. 683,907

Claims.

' This invention relates to alloys containing high percentages of copper which are capable of being hardened by certain processes of heat treatment, and more particularly copper base alloys 5 containing suflicient amounts of silicon and nickel to produce this hardening effect under certain heat treatment and a method or process of improving the resulting product.

In the patent to Corson 1,658,186 issued Febru-.

m ary 7, 1928 is described a process of heat treatment of copper base alloys containing certain amounts of silicon and nickel which comprises heating the alloy to a high temperature (from 750 to 975 C.) and holding it there for agiven time, then quenching and reheating to a temperature of between 250 C. and 600 C. and holding at this temperature for a given time.

It was found that in heating alloys having a composition of approximately 0.1 to 1.5% sili- 20 con, 2.0% to 6.0% nickel and balance copper to the high temperatures involved in this heat treatment a skin or film develops on the metal which is termed birch bark as it peels 011, and is very undesirable. That is, a filmis formed on the 25 material having a copper color. It is a very thin film, only about one or two thousandths of an inch thick, and peels off in a manner very similar to'the bark of a birch tree. Hence the term birch bark effect. The occurrence of this film or 30 birch bark effect rendered the alloy impractical and useless.

I have discovered that the addition of certain amounts of aluminum to this alloy will eliminate this birch bark effect or formation of the 35 thin skin during the heat treatment and renders the alloy practical as far as surface conditions are concerned. I have found if I add from approximately 0.5% to 5.0% aluminum to this alloy-depending on the amount of silicon present I 40 can effectively prevent the formation of this skin in the heat treatment involving these high temperatures. Thus an alloy having a composition of approximately from 0.1% to 1.5% silicon, from 2.0% to 6.0% nickel, from 0.5% to 5% aluminum 45 and balance copper will not form this birch bark or peeling skin when heated to the high temperatures involved in this treatment. The aluminum also increases the workability of the alloy (particularly facilitating hot working) the 50 strength, and resistance to corrosion, and for this purpose the amount of aluminum may be increased to about 6.5% with the proportions of silicon and nickel remaining the same. With above 6.5% aluminum the alloy rapidly becomes 05 very hard and brittle and lacks ductility and workability so that it is unsuited for structural purposes.

Two preferred compositions which I have found very useful for certain purposes are (1) approximately 91.20% copper, 4.0% aluminum, 4.0% 5 nickel and 0.80% silicon; and (2) 88.10% copper; 6.50% aluminum, 4.50% nickel and 0.90% silicon. Approximately the latter composition is very satisfactory for such uses as motor boat shafts and the like.

I have also found that the extremely high heating temperatures prescribed for the heat treatment noted produced a very coarse structure, and I discovered that the addition of given amounts of iron keeps the grain size fine. I may add iron for this purpose in amounts from 0.1% to about 3.0% to refine the grain size. It also increases the strength and workability of the alloy. In adding the iron the copper content is decreased accordingly, so that the proportions of silicon, nickel and aluminum remain the same: Thus the alloy would be composed of from 0.1% to 1 .5% silicon, from 2.0% to 6.0% nickel, 0.5% to 6.5% aluminum, from 0.1% to 3.0% iron and balance copper. In the specific compositions above mentioned as (1) and (2) I prefer to make the addition of iron about 0.25%, so that these compositions as modified would be composed of approximately 90.95% copper, 4.0% aluminum, 4.0% nickel, 0.8% silicon and 0.25% iron; and approximately 87.85% copper, 6.5% aluminum, 4.5% nickel, 0.90% silicon and 0.25% iron.

I have found I may also further increase the workability of the alloy by adding from 0.1% to 1.0% manganese, and may increase the fluidity of the metal in casting by adding from 0.1% to 1.5% tin. In each case in the addition of manganese and tin the amount of copper would be decreased accordingly with the proportions of silicon, nickel, aluminum and iron remaining as above given. The preferred amount of manganese and tin to beadded to the specific compositions above noted with the iron would be approximately 0.50% for each element. These specific compositions would then be composed of approximately 90.45% copper, 4.0% aluminum, 4.0% nickel, 0.8% silicon, 0.25% iron and 0.50% manganese; approximately 87.35% copper, 6.5% aluminum, 4.5% nickel, 0.90% silicon, 0.25% iron, and 0.50% manganese; approximately 89.95% 30 copper, 4.0% aluminum, 4.0% nickel, 0.8% silicon, 0.25% iron, 0.50% manganese and 0.50%

' tin; and approximately 86.85% copper, 6.5% aluvminum, 4.5% nickel, 0.90% silicon, 0.25% iron,

0.50% manganese, and 0.50% tin.

v4. A copper base alloy composed of approximately 87.85% copper, 6.5% aluminum, 4.5% nickel, 0.90% silicon, and 0.25% iron.

5. A copper base alloy which has been hardened by heat treatment and characterized by absence of the birch bark" effect as a result of the heat treatment, comprising 86% to 97.4% copper, from 0.1% to 1.5% silicon, from 2% to 6% nickel and aluminum from 0.5% to 6.5%.

HERBERT C. JENNISON. 

